Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$116.86	6.863%	$124.8801	$124.88	$124.90	$124.90
Purchase #2	$41.57	4.328%	$43.3691	$43.37	$43.35	$43.40
Purchase #3	$122.36	4.484%	$127.8466	$127.85	$127.85	$127.80
Purchase #4	$50.35	3.348%	$52.0357	$52.04	$52.05	$52.00
Purchase #5	$169.35	9.577%	$185.5686	$185.57	$185.55	$185.60
Purchase #6	$229.86	3.245%	$237.319	$237.32	$237.30	$237.30
Purchase #7	$215.73	8.610%	$234.3044	$234.30	$234.30	$234.30
7 purchase totals =	$946.08		$1,005.3235	$1,005.33	$1,005.30	$1,005.30